Portable terminal devices have recently become capable of causing a plurality of application programs to be executed simultaneously. The use case of “doing one thing while doing another thing”, such as music playback by a music reproduction application running in the background while checking a weather report by a weather application running in the foreground, is becoming more common. Accordingly, the power consumption of portable terminal devices is increasing. It is thus becoming an important issue to reduce power consumption.
In the above circumstances, a setup of dynamically controlling the operating frequency of a CPU in a range from the upper limit to the lower limit of the operating frequency of the CPU in accordance with the processing load on the CPU to reduce power consumption has been developed. In this setup, for example, if the processing load on a CPU decreases, the operating frequency of the CPU automatically decreases; whereas if the processing load on the CPU increases, the operating frequency of the CPU automatically increases.
Japanese Laid-open Patent Publication Nos. 01-292416 and 2010-39791 disclose examples of the related art.